diff --git a/packages/core/src/providers/probe.ts b/packages/core/src/providers/probe.ts
index 0a82346..1cf9387 100644
--- a/packages/core/src/providers/probe.ts
+++ b/packages/core/src/providers/probe.ts
@@ -1076,18 +1076,7 @@ function isProtocolSupported(
     if (/not found|unknown endpoint|unknown route|no route/.test(normalized)) {
       return false;
     }
-    if (protocol === "openai_responses") {
-      return /model|max_output|max output|input|required/.test(normalized);
-    }
-    if (protocol === "openai_chat_completions" || protocol === "anthropic_messages") {
-      return /model|max_tokens|messages|required/.test(normalized);
-    }
-    if (protocol === "gemini_generate_content") {
-      return /contents|generatecontentrequest|generationconfig/.test(normalized);
-    }
-    if (protocol === "gemini_interactions") {
-      return /model|input|required|interaction|generation_config|generationconfig|system_instruction/.test(normalized);
-    }
+    return true;
   }
 
   return false;
diff --git a/tests/main/provider-probe.test.mjs b/tests/main/provider-probe.test.mjs
index 9a650ee..4505486 100644
--- a/tests/main/provider-probe.test.mjs
+++ b/tests/main/provider-probe.test.mjs
@@ -43,7 +43,7 @@ test("protocol support probe keeps auth-only fallback for unhinted endpoints", (
   );
 });
 
-test("protocol support probe treats Gemini contents validation as Gemini support only", () => {
+test("protocol support probe treats HTTP 400 validation as protocol support", () => {
   const message = "HTTP 400: * GenerateContentRequest.contents: contents is not specified";
 
   assert.equal(
@@ -52,11 +52,11 @@ test("protocol support probe treats Gemini contents validation as Gemini support
   );
   assert.equal(
     isProviderProtocolEndpointSupportedForProbe(400, message, "openai_chat_completions", ["openai_chat_completions"]),
-    false
+    true
   );
 });
 
-test("protocol support probe treats Gemini Interactions input validation as Interactions support", () => {
+test("protocol support probe treats HTTP 400 input validation as protocol support", () => {
   const message = "HTTP 400: Gemini Interactions request requires input.";
 
   assert.equal(
@@ -65,6 +65,15 @@ test("protocol support probe treats Gemini Interactions input validation as Inte
   );
   assert.equal(
     isProviderProtocolEndpointSupportedForProbe(400, message, "gemini_generate_content", ["gemini_generate_content"]),
+    true
+  );
+});
+
+test("protocol support probe still rejects HTTP 400 route misses", () => {
+  const message = "HTTP 400: unknown route";
+
+  assert.equal(
+    isProviderProtocolEndpointSupportedForProbe(400, message, "openai_chat_completions", ["openai_chat_completions"]),
     false
   );
 });